In the prior art, the bottom surface of a card guide or card slot typically has a flat configuration and the data pickup element of the transducer mounted adjacent to the card guide is positioned at a fixed distance from this bottom surface. Accurate reading of a data stripe on a data card passed though the card slot is dependent on maintaining the bottom edge of the card in contact with the bottom card guide surface. If the card is swiped through the card guide at an angle, with just a corner in contact with bottom guide surface during a portion of the complete path of the card through the reading location, data reading errors are typically produced if the angle of the card edge relative to the bottom guide surface is sufficient to displace a substantial portion of the data track above the position of the data pickup element for that data track. Such data reading errors force the operator to swipe the card through the reader a second time.
This problem with read errors due to angled card swiping is especially exacerbated in card readers with short card slot length on the order of the length of the data card itself or less as is the case, for example, with use of a card reader in a hand held, battery powered unit, of a shirt pocket size. Depending on how the card is being gripped by the operator of the terminal and the swiping motion used, the card may start out with the bottom edge in full contact with the bottom edge of the card guide, but then start to pivot about one of the corners of the card as the card is being swiped. In some cases the entire swipe may occur with only one corner of the card in contact with the bottom guide surface.